1. Field of the Invention
The present invention relates to a bumper reinforcement structure, and in particular, to a bumper reinforcement structure provided at a front bumper or a rear bumper of a vehicle such as an automobile or the like.
2. Description of the Related Art
Conventionally, a bumper reinforcement is mounted to a front bumper or a rear bumper of a vehicle such as an automobile or the like. An example of such a bumper reinforcement structure is disclosed in Japanese Utility Model Application Laid-Open (JP-U) No. 61-109808.
As illustrated in FIG. 9, in this bumper reinforcement structure, an upper projecting portion 104A which extends upwardly and a lower projecting portion 104B which extends downwardly are formed at a bumper reinforcement 104 in order to support a bumper 102, which is wide in the vertical direction of the vehicle, to a side frame 100. A vertical direction central portion 104C of the bumper reinforcement 104 is connected to the side frame 100 via a bracket 106 having a mounting portion 106A which extends in the longitudinal direction along the side frame 100.
However, in this bumper reinforcement structure, at the time of a collision, load is applied to one of the upper projecting portion 104A and the lower projecting portion 104B of the bumper reinforcement 104. When the central position of load inputted from the bumper reinforcement 104 shifts upwardly or downwardly with respect to the axial center of the side frame 100, an upward or downward bending moment is generated at the front portion of the side frame 100, and the side frame deforms by bending and buckling without being deformed by axial compression. As a result, the energy absorbing ability at the side frame 100 deteriorates.
In this reinforcement structure, the mounting portion 106A of the bracket 106 is rigidly joined to a front portion 100A of the side frame 100 by bolts 108 and nuts 110 at two fixing portions which are formed with a predetermined interval therebetween in the longitudinal direction of the vehicle. As a result, at the time of a collision, at a front portion 100A of the side frame 100 which is rigidly joined, it is difficult for the mounting portion 106A of the bracket 106 to deform by axial compression. Therefore, the range of axial compressive deformation of the side frame 100 becomes small, and the energy absorbing ability of the of the side frame 100 deteriorates.